There is disclosed herein a guide device, with a wedge sliding surface, which finds application in bulk conveyors and is designed to be placed upstream from the lateral and central guides.
As used herein, the term bulk conveyors is intended to encompass belt conveyors, chain conveyors, roller conveyors and any device that defines a moving plane.
Guides are known to be used to retain and direct the items handled by the belt and chain conveyors.
The guides define sliding surfaces, which are substantially and/or generally orthogonal to the moving plane, and extend in the desired item handling direction.
The guide may extend along a path that may form a straight line, an open broken line or a curve, as needed.
Particularly, the use of lateral guides (also known as “side walls” or “roller units”) and central guides (also known as “partition guides” or “double sided roller units”).
The lateral guides may be placed both on sections with constant item flow direction and on sections with changing item flow direction.
The central guides are placed, for instance, at branch points of conveyor lines, i.e. where an item flow is to be divided into two distinct flows.
The lateral guides have one sliding surface only, whereas the central guides have two opposite and substantially and/or generally parallel sliding surfaces.
The sliding surfaces of the lateral or central guides are formed by a plurality of rolling bodies, which are idly mounted to parallel shafts; these rolling bodies may be, for example, cylindrical rollers, spheres or ellipsoids of revolution.
Lateral guides with idle running rollers are disclosed in patents EP 0 787 666 B1, EP 0 894 745 B1 and EP 0 931 737 A1.
Central guides with idle running rollers disposed on two opposite sides are disclosed in patents EP 1 340 698 A1 and EP 1 905 708.
The use of lateral and central guides with sliding surfaces defined by idle rolling bodies reduces friction and allows a more regular feed of the item flow, while limiting the risks of bridging.
The guides with idle rolling bodies have a first end (or head), designed to face against the item feed direction, and a second end (or tail), opposite to the first end, designed to face toward the item flow direction.
The lateral and central guides have a substantially and/or generally constant cross section.
At their heads, the guides form a “step change” of the lateral edges that define the cross section through which the flow of items handled by the conveyor moves.
This step change at the guide heads hinders the flow of the items handled by the conveyor and may also cause damages to the surfaces of the handled items, such as scores and scratches.
In order to reduce the resistance to the feed of the conveyed items at the heads of the guides, it is known to add guide devices before the guide heads, which have a substantially and/or generally wedge-shaped slide guide surface.
As used herein, the tem “wedge shaped” encompasses guide devices in which the side edges that define the cross section for the passage of at least one flow of items handled by the conveyor are modified in substantially and/or generally progressive fashion (according to a monotone function).
Particularly, the term “wedge shaped” encompasses guide devices having two symmetrically extending guide surfaces, which converge at one end and end have two parallel sections at the opposite end (such type of wedge-shaped guides being designed to be installed upstream from the central guide, relative to the flow of the conveyed items).
In this case, the converging portion of the sliding surface may have a substantially and/or generally “V” or “U” or ogival-shaped profile.
Furthermore, the term “wedge shaped” also encompasses guide devices that define a single guide surface, substantially and/or generally having an inclined, arched or semi-ogival initial section and a section parallel to the direction of extension of the guide device (in which case the wedge-shaped guide is mounted upstream from a lateral guide).
The prior art guide devices with wedge guide surfaces, located upstream from the central guides have a generally/substantially prismatic or ogival shape, or anyway have a narrow initial portion for receiving the item flow, and a wider final portion (whose width is substantially and/or generally equal to that of the central guide).
The guide devices with wedge sliding surfaces, located upstream from the lateral guides may comprise semi-ogival bodies or bodies having a constant thickness, but shaped to define an inclined or half-arch shaped surface.
The wedge guide devices with slide guide surfaces are commercially known as “separation blocks” or “side plows” or “nose plows”.
Wedge-shaped guide devices for lateral or central guides are currently sold by the Italian company Rexnord Marbett s.r.l., under the names 50759 and 50760, and by the US company Solus Industrial Innovations LLC, e.g. under the names VG-686P-1.25 and VG-687NP-1.4.
Prior art guide devices with wedge slide guide surfaces still have a few drawbacks.
Particularly, they may be affected by problems such as damage to the surfaces of the handled items, or the labels on the handled items, when the items slip on the surfaces of the wedge guide devices while they are being conveyed.
An additional problem that may be encountered is the presence of irregularities in the flow of items.
The object of this invention is to obviate at least some of prior art problems and particularly those set out hereinbefore.